Fig. 3. Merotelic orientation of lagging chromosomes after microinjection of Mad1F10. PtK1 cells recovering from a nocodazole-induced mitotic block were microinjected with GST-Mad1F10 to inactivate the mitotic checkpoint and to induce precocious anaphase. Cells were followed by time-lapse microscopy and fixed in mid-anaphase if they possessed one or more lagging chromosomes. Cells were then immunostained for CREST and -tubulin. After immunostaining, cells were re-localized to verify if lagging chromosomes were merotelically oriented. Two cells showing lagging chromosomes after microinjection of GST-Mad1F10 are shown. The frame showing microinjection, the last frame photographed by time-lapse microscopy before fixation, the phase contrast/CREST overlay, and the CREST/-tubulin overlays are shown in the four columns. (A) Microinjected cell showing one merotelically oriented lagging chromosome at anaphase. (B) Microinjected cell showing multiple merotelically oriented lagging chromosomes. Asterisks indicate the tip of the needle at the moment of microinjection. Scale bars: 10 µm.

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